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  • Microwaving Wood

    Can someone explain the process of microwaving green wood after the initial turn and then finishing it right away? I have seen several people that do this but can't find an explanation on it.
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  • #2

    Re: Microwaving Wood

    Its trial and error, but do it slowly, I imagine because all wood is different so is the time you can have it in a microwave.

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    • #3

      Re: Microwaving Wood

      Have a look at: https://www.woodworkersinstitute.com...rowaving-wood/

      I did a little drying with the microwave but then couldn't be bothered and just let them dry normally. I don't think I used the plastic film. As bkrits said, do it slowly and I would not start with the article's 6 minutes right away. Of course there will be lots of moisture boiled off at first and as the wood dries there will be less. Be careful, the wood can be very hot!!!! A scale is a handy method of checking your progress. The weight should drop quickly and then taper off as the wood approaches dry. When there is no change then it is dry. Moisture meter works too.

      It is just a method of drying the wood more quickly and then jumping to the second turning or finishing stage if you took it down to the finished sizes on the first turning. This can give some interesting shapes when the thin wood dries because it will warp. Would warp even without the microwaving. Personally, I like the turned twice method because it is easier to get a real smooth finish when turning/sanding dry wood rather than wet wood.

      billh

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      • #4

        Re: Microwaving Wood

        Key factor is to set microwave on DEFROST .. use that setting only. Time is relevant to size / weight but usually never longer then 2.5 mins, weigh before starting, when article is dry it will cease loosing weight, working in grams is easier, make sure it cools between cycles.

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        • #5

          Re: Microwaving Wood

          A lot depends on how powerful the microwave is, and it works better with a turntable. But to help alleviate that the way to go is to put the wood in a loosely closed plastic bag. Do not use a zip bag the steam generated has to be able to escape. So place the wood in the bag (I use a plastic grocery bag) Tuck the open end under the package and place it on the turntable. Use highest power setting and set timer for 2 minutes. Put on some thick work gloves and remove the package, take out the wood, then turn the bag inside out and put the wood back in and repeat the process. Always weigh the wood at each session and when the weight becomes stable the wood is as dry as it will go. If you carry on there will be charring inside the wood and possible a fire so the weighing is critical. I always stop when the weight difference is very minimal and check it with a moisture meter and find 12% is about right.
          If there's no turntable then stack the microwave totally full and forget the plastic. Zap at high power and let cool completely before doing it again. Again use weighing to determine progress. This method should only be used with rectangular blanks so you eliminate as much air space as possible.

          The plastic method works with wood of any shape or size. My failure rate is normally about 1-2%, as in failure = cracking
          HTH

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          • #6

            Re: Microwaving Wood

            ...and don't use the kitchen microwave...

            Noel
            "Being so impressed with the beauty of nature, I never cease to be amazed at how the
            'touch of the human hand' can transform it into another kind of beauty that is so uniquely human.
            "
            John Snow, Outdoorsman and Retired Teacher

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            • #7

              Re: Microwaving Wood

              i use a MW regularly for drying turning pieces, mostly pen sized pieces but some bowls too
              i give enough mw time to get it hot but not too hot to handle with bare hands, then i let it cool completely sitting on a shelf
              then repeat several times. i track the weight on a small kitchen scale, the weight loss can be considerable especially during the first couple of cycles
              i stop when it stops losing weight, then let the blank sit for a day(pen blank) or up to a week for a bowl blank
              a totally green pen blank will take a dozen 1 minute cycles, considerably more of course for a bowl

              i got a piece of green tulipwood with some spalting, i quatered a piece of the log and i'll be drying over a day or two, i dont sit and wawtch it dry, i just MW it once in a while when i remember to do it!!

              Click image for larger version

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              fresh off the log, it weighs 305 grams, i gave it 2 minutes on high in my cheapie old oven and its slightly steaming but can be handled with bare hands.
              i'll post again as it dries, this post was done at 8pm
              Last edited by stevem; 10-26-2019, 08:19 PM.
              Steve in Richmond and WoodBob like this.
              my shop is a beaver lodge
              steve, sarnia, ont




              1940's Craftmaster Lathe

              https://www.facebook.com/artistryinwoodca/

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              • #8

                Re: Microwaving Wood

                Originally posted by WoodBob View Post
                Can someone explain the process of microwaving green wood after the initial turn and then finishing it right away? I have seen several people that do this but can't find an explanation on it.
                Bob the microwaves agitate the water inside the wood so it turns into steam, and can more quickly move out of the wood, as more water is removed the wood will shrink and can easily split and often does, but for it being hot it is more pliable to some extend and the lignin will let the fibers move somewhat, however it can also easily get TOO hot when most or all of the water is gone and start to burn on the inside, happens easily and quickly, see you can’t tell how dry the wood is inside, and people want to have it dry quickly.

                I have tried the use of the microwave, even though I was not in a hurry to get the piece dry, anyway I did the short duration heating cycles and then let the piece cool off, after a couple of cycles it smelled like wood smoke, nothing to see on the outside but as I was holding it the smoke started to come out of the wood, short story was that the wood had turned into charcoal on the inside, not a success.

                Gave up on that idea, but a few years after this trial, I had turned a dozen or more Manitoba Maple bowls, fair size but able to fit into my microwave, the thought was that maybe I could just dry a few of the bowls partly in the microwave, did 6 IIRC, anyway, they looked fine after just on short cycle maybe 2 minutes intros old Sears 800 watt or so microwave, (picked up on the side of the road with the City spring cleanup day), so put them and the other ones in brown paper bags and let them dry.

                Few weeks later I removed the bowls out of the brown Paper bags to have look at them and compare the pre-dried and the other ones, well it was not a success .

                The ones that had been partially dried had lots of small splits in them, and the other ones did not, couple pictures here where I have one of the bowls with all the splits in them (filled with brass metal filings) and a couple other ones that are just my regular outcome after drying in a Brown Paper bag for a couple months, it was the last time I considered using a microwave to dry or even partially dry a good turning to have it turn into scrap or firewood .

                Click image for larger version  Name:	split Manitoba Maple bowl.jpg Views:	0 Size:	76.5 KB ID:	1257014
                Click image for larger version  Name:	Manitoba Maple bowl with handles.jpg Views:	0 Size:	62.3 KB ID:	1257015
                Click image for larger version  Name:	Manitoba Maple bowl.jpg Views:	0 Size:	56.7 KB ID:	1257016
                For what people tell you, and try to have you believe them, well see the next picture where some smart guy stuck a piece of wood in a regular convection oven and dried it, see what he tells us, yup. he has a piece of wood after drying it, it is full of splits, large splits, and tries to say you could use that nice dry and wonderful dry wood to make all kinds of things, even turn things from it, etc. .

                Click image for larger version  Name:	oven dried and split wood.jpg Views:	0 Size:	50.4 KB ID:	1257017
                Here are a couple more where turners show what can happen in a heart beat.

                Click image for larger version  Name:	Microwaved and split wood.jpg Views:	0 Size:	34.5 KB ID:	1257018Click image for larger version  Name:	internial burned and split.jpg Views:	0 Size:	32.9 KB ID:	1257019
                Another one.

                Click image for larger version  Name:	another microwave dried and burned wood.jpg Views:	0 Size:	23.9 KB ID:	1257020

                Can it be done, yes but it takes a lot more time, especially the cooling off period, not just a couple of minutes, it will not do, weigh the piece every time before and after a cycle, and stop if the weight does hardly change at all.
                Last edited by Leo Van Der Loo; 10-29-2019, 08:52 PM.

                Have fun and take care
                Leo Van Der Loo

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                • #9

                  Re: Microwaving Wood

                  the piece of tulip woood that i did lost a 1/3 of its weight in 12 2 minute cycles spread over three days, dropping to 209 grams from 305. the last cycle did nothing to the weight and after sitting overnight it gained 5 grams!

                  its slightly twisted/warped and i will cut it into pen blanks in a week or so

                  it does take patience!

                  my MW(in the shop) is an old beatup thing, i dont know the wattage but heating up a cup of coffee in it takes twice as long as the 1200 watt MW in the kitchen, so 600 watt? i guess! no turntable

                  just a side note, you see what happens when you nuke a piece of spruce burl, LOL. hint, do it in an old baking dish!!
                  Last edited by stevem; 10-29-2019, 07:56 PM.
                  my shop is a beaver lodge
                  steve, sarnia, ont




                  1940's Craftmaster Lathe

                  https://www.facebook.com/artistryinwoodca/

                  Comment


                  • #10

                    Re: Microwaving Wood

                    Are there any health reasons why I should not use my kitchen microwave? I don't need another piece of equipment in the shop!

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                    • #11

                      Re: Microwaving Wood

                      I doubt if there is any health issue other than your wife, if you have one, may not buy the idea that this is a good use for the kitchen microwave. You may find there is a slight odor left in the oven but it will not linger long.
                      billh

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                      • #12

                        Re: Microwaving Wood

                        haha, using the kitchen MW would definitely be a health hazard in our house!!
                        besides i like having it in the shop, i can run another cycle anytime during my shop time

                        sappy woods will make a helluva mess, primarily soft woods of course. the spruce burls i did spatted all over and left a 1/4 inch of sticky gooey sap in the baking dish plus it stank
                        on the other hand, soft maple has a nice aroma of maple syrup! same with fruit woods.
                        my shop is a beaver lodge
                        steve, sarnia, ont




                        1940's Craftmaster Lathe

                        https://www.facebook.com/artistryinwoodca/

                        Comment

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